1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine or a printer for forming output sheet bundles each inserted with one or more tabbed sheets, and relates to a control method for the image forming apparatus and a storage medium storing a program for executing the control method.
2. Description of the Related Art
Conventionally, there has been proposed an image forming apparatus having a tabbed sheet mode for creating output sheet bundles in each of which one or more tabbed sheets are inserted at positions corresponding to designated pages for the purpose of adding headings or dividing into chapters.
In the tabbed sheet mode, tabbed sheet bundles each comprised of a plurality of tabbed sheets which are different in tab position from one another are generally used. In an example of FIG. 14, a tabbed sheet bundle is comprised of five tabbed sheets. When output sheet bundles each inserted with three tabbed sheets are produced by using tabbed sheet bundles each comprised of five tabbed sheets, two surplus tabbed sheets are produced in each bundle. To deal with this matter, a user is required to set tabbed sheet bundles, from which surplus tabbed sheets have been removed in advance, to an image forming apparatus. However, this is laborious.
Accordingly, image forming apparatuses have been proposed that are configured to automatically discharge surplus tabbed sheets to the outside each time an output sheet bundle is produced. For example, there is an image forming apparatus configured to discharge output sheet bundles and surplus tabbed sheets to different discharge trays (see, Japanese Laid-open Patent Publication No. 2002-3063).
However, with the image forming apparatus that discharges surplus tabbed sheets after creation of each output sheet bundle, it is necessary to start image formation for the next output sheet bundle after waiting for discharge of the surplus tabbed sheets. In particular, in the case of a double-sided printing job in which tabbed sheets are inserted into between double-sided printed recording sheets to produce a plurality of output sheet bundles, it is necessary, after a last recording sheet used for creation of each output sheet bundle is double-sided printed and discharged to the outside of the apparatus, that a conveyance mode must be changed, surplus tabbed sheets must be discharged, and image formation on recording sheets used for creation of the next output sheet bundle must be started. As a result, the productivity in creating output sheet bundles is lowered.
A double-sided printing job is primarily performed in such away that a sheet interval does not become excessively large at a break between output sheet bundles. For example, double-sided circulation control is made in which a top sheet used for creation of output sheet bundle is started to be fed, without waiting for completion of double-sided printing on a last sheet used for creation of preceding output sheet bundle. As a result, a sheet interval does not become excessively large at a break between output sheet bundles even during the double-sided printing job, whereby high productivity can be maintained.
However, if surplus tabbed sheets are discharged after creation of each output sheet bundle as in the aforementioned conventional image forming apparatus, it is necessary to discharge surplus tabbed sheets after waiting for completion of double-sided printing and discharge of the last sheet used for creation of output sheet bundle. As a result, double-sided circulation control is disconnected at a break between output sheet bundles, and therefore the productivity of image formation is lowered.